linux-kernel - Re: [PATCH v1 0/3] Metric related performance improvements

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Message-ID: <aCOewZobRD1dPrl4@x1>
Date: Tue, 13 May 2025 16:34:25 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Ian Rogers <irogers@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	James Clark <james.clark@...aro.org>, Xu Yang <xu.yang_2@....com>,
	John Garry <john.g.garry@...cle.com>,
	Dominique Martinet <asmadeus@...ewreck.org>,
	Thomas Richter <tmricht@...ux.ibm.com>,
	Weilin Wang <weilin.wang@...el.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/3] Metric related performance improvements

On Wed, Apr 09, 2025 at 11:49:16PM -0700, Namhyung Kim wrote:
> Hi Ian,
> 
> On Wed, Apr 09, 2025 at 09:45:29PM -0700, Ian Rogers wrote:
> > The "PMU JSON event tests" have been running slowly, these changes
> > target improving them with an improvement of the test running 8 to 10
> > times faster.
> > 
> > The first patch changes from searching through all aliases by name in
> > a list to using a hashmap. Doing a fast hashmap__find means testing
> > for having an event needn't load from disk if an event is already
> > present.
> > 
> > The second patch switch the fncache to use a hashmap rather than its
> > own hashmap with a limited number of buckets. When there are many
> > filename queries, such as with a test, there are many collisions with
> > the previous fncache approach leading to linear searching of the
> > entries.
> > 
> > The final patch adds a find function for metrics. Normally metrics can
> > match by name and group, however, only name matching happens when one
> > metric refers to another. As we test every "id" in a metric to see if
> > it is a metric, the find function can dominate performance as it
> > linearly searches all metrics. Add a find function for the metrics
> > table so that a metric can be found by name with a binary search.
> > 
> > Before these changes:
> > ```
> > $ time perf test -v 10
> >  10: PMU JSON event tests                                            :
> >  10.1: PMU event table sanity                                        : Ok
> >  10.2: PMU event map aliases                                         : Ok
> >  10.3: Parsing of PMU event table metrics                            : Ok
> >  10.4: Parsing of PMU event table metrics with fake PMUs             : Ok
> >  10.5: Parsing of metric thresholds with fake PMUs                   : Ok
> > 
> > real    0m18.499s
> > user    0m18.150s
> > sys     0m3.273s
> > ```
> > 
> > After these changes:
> > ```
> > $ time perf test -v 10
> >  10: PMU JSON event tests                                            :
> >  10.1: PMU event table sanity                                        : Ok
> >  10.2: PMU event map aliases                                         : Ok
> >  10.3: Parsing of PMU event table metrics                            : Ok
> >  10.4: Parsing of PMU event table metrics with fake PMUs             : Ok
> >  10.5: Parsing of metric thresholds with fake PMUs                   : Ok
> > 
> > real    0m2.338s
> > user    0m1.797s
> > sys     0m2.186s
> > ```
> 
> Great, I also see the speedup on my machine from 32s to 3s.
> 
> Tested-by: Namhyung Kim <namhyung@...nel.org>

I'm collecting this for v2 as well, ok? Holler if you disagree.

- Arnaldo